The primary purpose of this study is to quantify infarct size and assess the efficacy of electrocardiography to predict infarct size. The objective is to correlate quantitative electrocardiographic criteria with quantitative pathological evidence of anterior, inferior, and nontransmural myocardial infarction. Sensitivity and specificity of polarcardiography, vectorcardiography and 12-lead electrocardiography will be determined. The analysis of the electrocardiograhic criteria will both be done by two investigators and computer analysis. The sample size will consist of 60 subjects with myocardial infarction and 30 subjects without myocardial infarction. Optimal polar coordinate discriminators of the pathological characteristics of the myocardial infarction lesion will be determined by multivariate analysis techniques. Pathological techniques to be employed are: a) nitro-blue-tetrazolium incubation of gross sections of myocardium to indicate areas of loss of myocardial dehydrogenase as occurs in myocardial infarction; b) post-mortem angiography; c) quantitative measurement of coronary stenosis by planimetry; d) quantitative histological assessment of myocardial injury using microscopic criteria; and e) measurement of the location of the infarct on the wall area (inferior, anterior, etc.) and the transmural versus nontransmural extent. Polarcardiograms will be taken on ten dogs before and after experimental left coronary artery occlusion to determine if the polarcardiographic criteria of anterior myocardial infarction defined in humans is analogous to an animal model. This has important implications for future experimental research in polarcardiography.